1. Technical Field
Example embodiments of the following disclosure relate to a technology for estimating a pose of a camera based on three-dimensional (3D) information included in an image.
2. Background Art
An augmented reality refers to a technology for displaying graphic objects, or additional information, and a real image captured by a camera in an overlapping manner. In order to implement an accurate augmented reality, however, accurate estimation of a pose of a camera, that is, a location and a direction of the camera may be important. In order to estimate the location or direction of the camera, a predetermined marker may be used. Further, a method of estimating a relative location of a current camera in comparison to a location of a reference camera by disposing, in a real space, a pre-defined reference object, for example, a two-dimensional (2D) planar image or a three-dimensional (3D) model may be used.
FIG. 1 illustrates examples of a marker according to an art.
Referring to FIG. 1, an upper part 110 of FIG. 1 illustrates markers that are prepared in advance, and may be provided in an artificial form, for example, Quick Response (QR) codes. A lower part 120 of FIG. 1 illustrates an example of using a 2D or 3D reference object existing naturally in a real image, as a marker. In the lower part 120 of FIG. 1, a monitor, a keyboard, and a picture disposed on the table may be used as reference objects.
As shown in the lower part 120 of FIG. 1, a case in which a 2D or 3D object is used as a marker may be classified as being marker-less in terms of using a natural reference object existing in a real space. However, in reality, such a case may correspond to a process using a marker since preparations, for example, storing the reference object as a marker in a database, and the like, may be required. In the lower part 120 of FIG. 1, point features marked with a plus sign (+) may be stored in the database in order to use the reference objects as markers.
Accordingly, in order to utilize an augmented reality technology, absent a delay, in a desired location and at a desired time without such advance preparations, marker-less camera tracking and matching without use of a reference object may be required.
In general, in an augmented reality technology, camera tracking and matching may be performed mainly using point features based on intensity information in a color image, irrespective of whether a marker is used. In this instance, a limitation that illumination conditions shall be constant and rich texture shall be used to find distinctive point features may exist in utilizing the intensity information of the color image.
In parallel tracking and mapping (PTAM), a representative example of a marker-less augmented reality technology, a method of finding point features from a color image, generating a map with respect to a 3D space using a correspondence between point features for each frame, and estimating a pose of a camera based on the generated map may be used. In particular, since a five point algorithm may be used to generate the map initially, at least five corresponding point features may need to be extracted. When texture is poor, extraction of point features may fail, and an augmented reality system may not operate normally.